Pneumatic riveter



Patented .lune 25, 1923..

ERNST REHEELD, 0E BERLIN, GERMANY, AsSIGNoR To DEUTSCHE WERKE.AKTIEN-` GESELLSCHAFT, or BERLIN, GERMANY, A CORPORATION or GERMANY.

PNEUMATIC RIVETER.

Application filed December 27, 1921. Serial No. 525,191.

T o all who-m t may concern Be it known that l, ERNST REHFELD, aA`

citizen of the German Republic, residing at Berlin, Germany, have invented new and useful Improvements in Pneumatic Rivet- ,ers, of which the following is a Vspecificathe riveting tool.

Pneumatic riveters are yprovided with a valve chamber forming prolongation of the cylinder and must have proper valve con trol for the instroke and outstroke of the` piston; the valve must not only be Secured in both its end positions by air pressure, but it must be capable of quick reversing motion, at the instroke, under air compression from the cylinder during a short piston movement, because otherwise the valve would require an undesirable longitudinal extension of the cylindrical body.

In the improved riveter, having a tubular valve provided with the usual four working faces, the movement of thevalve is` so Controlled that, of` the-four working faces,` the two faces which are active in `causing the rearward stroke or instroke of the piston, become exposed to the pressure of the air from theworking cylinder or barrel before the completion of the instroke andy thus are Started to move inopposite direction, after which the one of said `two faces is exposed to live-air in order to complete the movement, while the other face is relieved of pressure, so that at the end of the instroke of the piston a reliable return movement of the valve for the power-stroke is effected through pressure on the corresponding active faces of the valve, one of which latter faces becomes relieved of pressure during the reversing movement, while the other face is kept under pressure in order to ensure the proper position of the valve for the powerstroke of the piston.

An embodiment of the invention is shown in the annexed drawings, in which Figures 1 and 2 are longitudinal central sections of a pneumatic riveter, partly broken away, showing the valve in two end positions. Fig. 8 is a section on line 3-3 of Fig. 2.

The numeral 1 denotes lthe handle with the usual admission for compressed air. 2

denotes the valve box, 3 is the tubular valve, 4 is the cylinder and 5 is the piston.- 6 denotesa rivetingtool which receives the impact from ythe piston 5. The compressed air' passes through a circular groove 7 into a circular channel 8 which communicates with passages 9 and 10. The valve 3 has perforations 11 above the projecting valve surface 12. 13 is a passage leading from the cylinder into the valve box 2 for leading air from the cylinder' against the surface b of" the collar 14 and to the step 15 ofthe valve" 3. The collar 14 provides the two opposite Surfaces a and b for the application of pneumatic pressure one of which surfaces brought into play at every reversing motion of the valve 3. 16 is aV circular groove in the valve 3 between the'surface Z) offthecollar 14 'and the step 15. 17 denotes a recess forming-.connection between the lower surface Z) of the collar 14 and the'step 15. 1S is a channel leading from the valvebox 2 through the wall of the cylinder 4to the lower end` into the space'c in front of the piston 5. 19` is a` circular groove in thc valve 3 between the step 12 and the surface a of the collar 14. 20 is a bore in thevalve boxw2 leading into a circular channel? 21 in communication with the exhaust port 22. 23 is a circular groove at the lower part ofthe valve box with bore24 which communicates with' the channell 21 and with the exhaust port 22. 1 25 and 26y are two superposed ports leading from the cylinder space le* into the passage 18, while 27 is an outlet from the cylinder to the outer air, which outlet may, however, be omitted.

The operation is as follows With the lowered position of the valve 8 and the piston 5 moving as indicated by the arrow, see Fig. 1, the circular channel 8 now opened by the valve supplies compressed air to the piston 5. The compressed air also enters the perforations 11 and presses on the upper surface of the step 12 of the valve, thus securing same in the lowered position. The other steps of the valve are cut off from the compressed air so long as the piston 5 obturates the openings 25 and 26. Vhen the piston descends below the opening 25, compressed air passes from the space lo* into the passage 13, enters by the circular groove 16 and recess 17 to both Sides of the step 15. In this manner only the surface b of the collar 14 is under pressure bethe step still remains exposedvto com-` pressed air entering from the groove 8 through the channel 9 because of the closing of 8 from the cylinder space 16X by the valve cation with the atmosphere.

3. Thus, the underside of the step 15 is under pressure and secures the valve in its elevated position.

`As soon as the upper surface a of the collar 14 during the ascent of the valve 3 passes the upper edge' of the bore 20, the lower edge of the step 12 will open the channel 10 which then supplies compressed air to the upper surface a of the collar 14 which now acts in opposition to the smaller under-edge of the step 15 so that, withoutthe valve being held less securely in its upper position, the subsequent lowering of same is facili tated and can be effected with very little pressure. n

Furthermore, in lifting the valve, the annular groove 23 is opened and brings the space lo* above the piston 5 into conm'iunip The compressed air channel 10opened by the groove 19 in valve 3 to the channel 18 in the valve box 2, allows fresh air to enter below the piston 5 and force same upward. l

As soon as the piston covers the annular groove 23, which had opened the exhaust into the atmosphere, the-air in the valvei chamber will become compressed and after a short travel of the piston, the air will press on the upper edge'of the step 12 so as to shift the valve with thev simultaneous help of the pressureuponfthesurface `t of the collar 14. When `the piston passes the bores 26 and 27, a quick release of air in the cylinder takes place. This exhaust through the bore 27 can be dispensed with, it serves only with short-stroked quick action tools which require both exhausting arrangements. Under ordinary circumstances the rshifting down of the valve 3 opens a path by way of the channel 18, annular groove 19, bore 20, annular space 21 and exhaust port 22 for exhausting the cylinder as well as the surface of the collar 14 land the edge of the step 15. f

A pneumatic tool comprising a cylinder and a piston reciprocating therein, a compressed air conduit and a tubular valve forming an extension of the cylinder and in which said piston is adapted to travel controlling the inlet and exhaust for both the in and out stroke, said valve having two Vpairs of surfaces adapted to be vacted upon bythe compressed air from the said air conduit, one surface of one pair being adapted Ito shift the valve forwardly, the other 'surface of said pair being adapted ,to hold the valve forwardly, one surface of the other pair being adapted to shift the valve rearwardly, the other surface of said second pairbeing adapted to hold the valve rearwardly, the pressure on one surface of one pair of surfaces being relieved when pressure is applied to one surfaceof the other pair, and

the pressure to the holding surface of the first pair being cut off when lpressure is alpplied to the holding surface of the other pair, ports and passages connecting the cylinder and said surfaces and controlledby theypisf-v ton whereby air is admitted 4to actuate 'said piston.

ERNST vilueniuenu.` 

